The apparently simple dihydrogen formation from protons and electrons (2H+ + 2e- ↔ H2) is one of the most challenging reactions in nature. It is catalyzed by metalloenzymes of amazing complexity, called hydrogenases. A better understanding of the chemistry of these enzymes, especially that of the [NiFe]-hydrogenases subgroup, has important implications for production of H2 as alternative sustainable fuel. In this work, reactivation mechanism of the oxidized and inactive Ni-B and Ni-A states of the [NiFe]-hydrogenases active site has been investigated using density functional theory. Results obtained from this study show that one-electron reduction and protonation of the active site promote the removal of the bridging hydroxide ligand contained in Ni-B and Ni-A. However, this process is sufficient to activate only the Ni-B state. H2 binding to the active site is required to convert Ni-A to the active Ni-SIa state. Here, we also propose a reasonable structure for the spectroscopically well-characterized Ni-SIr and Ni-SU species, formed respectively from the one-electron reduction of Ni-B and Ni-A. Ni-SIr, depending on the pH at which the reaction occurs, features a bridging hydroxide ligand or a water molecule terminally coordinated to the Ni atom, whereas in Ni-SU a water molecule is terminally coordinated to the Fe atom, and the Cys64 residue is oxidized to sulfenate. The sulfenate oxygen atom in the Ni-A state affects the stereoelectronic properties of the binuclear cluster by modifying the coordination geometry of Ni, and consequently, by switching the regiochemistry of H2O and H2 binding from the Ni to the Fe atom. This effect is predicted to be at the origin of the different reactivation kinetics of the oxidized and inactive Ni-B and Ni-A states

Breglia, R., Greco, C., Fantucci, P., De Gioia, L., & Bruschi, M. (2019). Reactivation of the Ready and Unready Oxidized States of [NiFe]-Hydrogenases: Mechanistic Insights from DFT Calculations. INORGANIC CHEMISTRY, 58(1), 279-293 [10.1021/acs.inorgchem.8b02348].

Reactivation of the Ready and Unready Oxidized States of [NiFe]-Hydrogenases: Mechanistic Insights from DFT Calculations

Breglia, Raffaella
Primo
;
Greco, Claudio
Secondo
;
Fantucci, Piercarlo;De Gioia, Luca
Penultimo
;
Bruschi, Maurizio
Ultimo
2019

Abstract

The apparently simple dihydrogen formation from protons and electrons (2H+ + 2e- ↔ H2) is one of the most challenging reactions in nature. It is catalyzed by metalloenzymes of amazing complexity, called hydrogenases. A better understanding of the chemistry of these enzymes, especially that of the [NiFe]-hydrogenases subgroup, has important implications for production of H2 as alternative sustainable fuel. In this work, reactivation mechanism of the oxidized and inactive Ni-B and Ni-A states of the [NiFe]-hydrogenases active site has been investigated using density functional theory. Results obtained from this study show that one-electron reduction and protonation of the active site promote the removal of the bridging hydroxide ligand contained in Ni-B and Ni-A. However, this process is sufficient to activate only the Ni-B state. H2 binding to the active site is required to convert Ni-A to the active Ni-SIa state. Here, we also propose a reasonable structure for the spectroscopically well-characterized Ni-SIr and Ni-SU species, formed respectively from the one-electron reduction of Ni-B and Ni-A. Ni-SIr, depending on the pH at which the reaction occurs, features a bridging hydroxide ligand or a water molecule terminally coordinated to the Ni atom, whereas in Ni-SU a water molecule is terminally coordinated to the Fe atom, and the Cys64 residue is oxidized to sulfenate. The sulfenate oxygen atom in the Ni-A state affects the stereoelectronic properties of the binuclear cluster by modifying the coordination geometry of Ni, and consequently, by switching the regiochemistry of H2O and H2 binding from the Ni to the Fe atom. This effect is predicted to be at the origin of the different reactivation kinetics of the oxidized and inactive Ni-B and Ni-A states
Articolo in rivista - Articolo scientifico
Scientifica
Physical and Theoretical Chemistry; Inorganic Chemistry; hydrogen; hydrogenase; density functional theory
English
Breglia, R., Greco, C., Fantucci, P., De Gioia, L., & Bruschi, M. (2019). Reactivation of the Ready and Unready Oxidized States of [NiFe]-Hydrogenases: Mechanistic Insights from DFT Calculations. INORGANIC CHEMISTRY, 58(1), 279-293 [10.1021/acs.inorgchem.8b02348].
Breglia, R; Greco, C; Fantucci, P; De Gioia, L; Bruschi, M
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10281/215018
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